P1623: LOW LEVELS OF 25(OH) VITAMIN D IN ADULT PRIMARY ITP PATIENTS
Authors: Theresa Schramm, Jasmin Rast, Michael Fillitz, Barbara Dixer, Peter Quehenberger, Dino Mehic, Cihan Ay, Ingrid Pabinger, Johanna Gebhart
Journal: HemaSphere (2023)

Topic: 33. Bleeding disorders (congenital and acquired) Background: Primary immune thrombocytopenia (ITP) is an orphan autoimmune disease, characterized by heterogeneous bleeding phenotypes, not necessarily connected to low platelet counts. 25-(OH) vitamin D (VD) has been reported to have immunomodulatory properties. Vitamin D deficiency (VDD) has been associated to more severe courses of ITP, especially in acute pediatric cases. Aims: The purpose of this study was to investigate VD levels in a large, well-characterized cohort of adult ITP patients and to look into possible association with disease duration, bleeding severity and platelet counts. Methods: One hundred and nineteen adult primary ITP patients (28 acute, 12 persistent, 79 chronic) and 20 age- and sex- matched healthy controls (HC) from the Vienna ITP Biobank (EC 1843/2016) were analyzed in regard to their VD status. Serum VD reference levels are between 75-250 nmol/L, levels below 75 nmol/L were categorized as VDD. Bleeding severity was recorded using a consensus-based ITP-specific bleeding assessment tool (SMOG Score). To investigate the influence of VD levels on bleeding severity and platelet counts and selected clinical and laboratory parameters, a linear regression analysis was performed. Results: ITP patients had lower median (IQR) VD levels than HC (49.1 (29.5-65.1) and 64.3 (52.9-79.5) nmol/L, p<0.01). Compared to HC, VD levels were lower in acute (43.2 (21.7-61.8) nmol/L), persistent (48.4 (29.6-60.3) nmol/L) and chronic (51.5 (36.2-69.4) nmol/L) ITP patients without a relevant difference between the patient groups. A slightly higher VDD rate was observed in ITP patients (n=99,83.2%) than in HC, (n=15, 75.0%, p=0.162). This difference was significant in the occurrence of severe VDD, as 60 (50.4%) ITP patients had VD levels <50 nmol/L and 30 patients (25.2%) had VD levels <30 nmol/L compared to 3 (15.0%, p=0.003) and 1 (5.0%, p=0.045) HC, respectively. Table 1 lists clinical and laboratory data of all ITP patients, ITP patients with VDD, normal VD, and HC. In VDD patients compared to those with sufficient VD the rate of women was lower (p= 0.002) and BMI was higher (p=0.025). No relevant differences in age, disease duration, bleeding severity, or platelet counts were observed between ITP patients with VDD or normal VD levels. In ITP patients, VD levels were not associated with bleeding severity (R2= 0.002, β= 0.045, p= 0.624), platelet counts (R2= 0.004, β= 0.065, p= 0.485), age, disease duration, BMI, or calcium levels (not shown). A dependence of VD by sex (R2=0.045, β= 0.213, p= 0.020) and ongoing treatment (R2=0.040, β= 0.201, p= 0.029) was observed in the total ITP cohort. Women presented higher median (IQR) VD than men (44.8 (35.1-74.3) vs 52.2 (26.9-58.7) nmol/L, p=0.043). Patients with treatment tended to have lower levels of VD (44.5 (27.8-63.0) vs 53.1 (36.2-73.2) nmol/L, p=0.110). Summary/Conclusion: In our cohort, ITP patients presented lower VD levels than HCs. VD levels did not correlate with platelet counts, in line with previous data, and also there was no association with bleeding severity. Whereas women and untreated ITP patients had lower VD levels, VD levels were not influenced by age, disease duration, BMI or calcium levels. We found no relevant effect of VD levels on ITP disease severity. The clinical relevance of VD levels in adults with primary ITP needs to be further elucidated in future investigations.The ITP biobank was supported by Novartis, Swedish Orphan Biovitrum (SOBI), MedMedia Verlag und Mediaservice GmbH and AMGEN GmbHKeywords: Immune thrombocytopenia (ITP), ITP